The overall objective of this project is to gain better understanding of the body protein losses which frequently accompany severe injury or surgical trauma and to find ways to minimize or reduce these losses, especially in older subjects. To this end we are investigating the effect of protein level and amino acid supplementation to young and old rats, and the differences in amino acid requirements of cells, in culture, from animals of various ages. It has been shown that the addition of arginine and glycine and of branched-chain amino acids will lower nitrogen (N) losses following trauma. We will now investigate interactions of dietary amino acids with trace elements, especially zinc, and mechanisms of the reduction of N losses through these supplementations. We will then attempt to combine the various factors which have been indicated to ameliorate N losses and test combinations of these in young and old rats. We also plan to search for explanations for differences in requirements for amino acids for optimal growth of kidney cells from young and old rats in primary cell culture. Finally, we will study the wound healing process by investigating type and quantity of different collagens synthesized during the week following trauma.